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TC4+ Arduino Shield
Quick Start Guide
April 20, 2019
Contents
1 Overview 2
2 Assembly (kit version) 3
3 Connecting to your roaster 5
4 Software 10
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Figure 1: The TC4+ board and its on-board components.
1 Overview
The TC4+ is an Arduino shield providing a 4-channel thermocouple interface
and driver logic for AC and DC loads. The main components on the board are
shown above in Figure 1. The next page shows all connectors and status LEDs
schematically. The most important components are:
• 4-channel thermocouple interface using high-resolution ADC with coldjunction compensation for accurate temperature monitoring.
• DC In and DC out screw terminals; voltage regulator to supply the Arduino from DC In; MOSFET to control DC Out.
• OT1 and OT2 screw terminals to control SSRs.
The rest of this guide will briefly describe how to assemble, connect and configure
the TC4+ board in common scenarios.
Important: This is only a quick start guide, and only about interfacing the
TC4+ board. It is not a guide on how to build your own coffee roaster. Do
your own research, especially regarding safety. The TC4+ is intended for use
by qualified professionals. If you are not qualified to work with mains electricity
and in fire safety, get professional help.
Important: The TC4+ includes several components that are very sensitive
to electrostatic discharge, including the ADC and temperature sensor in the
thermocouple interface, and the IRF540 MOSFET for the DC driver. Follow
appropriate procedures when handling the TC4+. Failure to do so may result
in damage to these components.
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Figure 2: Layout of TC4+ through-hole components.
2 Assembly (kit version)
If you purchased a TC4+ KIT, it will come with all surface-mount devices soldered, and loose through-hole components which you will have to solder yourself.
Figure 2 shows the location of these components in different colours:
• Dark Red: Stackable headers.
• Orange: Male headers; break apart as necessary. [1]
• Pink: Angled female header.[2]
• Blue/Turquoise: Screw terminals. [2]
• Yellow, labelled VREG: Voltage regulator. The kit comes with a R-78E5.0
switching regulator.
• Yellow, C12/C13: 10uf ceramic capacitors. C1/C2 are not used with the
R-78E5.0 switching regulator.
• Green, labelled TFAN: IRF540 transistor. Optionally fixed to board with
M3 screw.
Notes: [1] BT SEL (2x3, top left) and BT RST (1x2, bottom right) are for
jumpers, so male headers are required. For the I2C, IO2 and IO3 headers, a
different connector could be used if preferred.
[2] Included connectors are suggestions – any other 2.54mm / 5.08mm spaced
header could be used. For the Bluetooth board, an angled female 4/5 pin header
will have the Bluetooth module horizontal next to the TC4+ shield. For vertical
BT module, use a straight female 4/5 pin header.
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Bluetooth header
Thermocouple header
Power LED
BT SEL jumper
(set to BT Serial)
IO2 & IO3
headers
OT1 & OT2
status LEDs
I2C headers
BT HDR
SERIAL
IO2IO3
- OT2 + - OT1 +
BT SEL
OT1LED
OT2LED
I2C
TC4+
CH2- CH2+ CH1- CH1+ CH4- CH4+ CH3- CH3+
DIO45
GNDGND
SCL SDA 5V GND
INPUT
GND VIN
POWERLED
BT RST
FAN
DC+ DC-
OT1 & OT2
headers
DC input
DC (fan) output
BT RST jumper
(BT Reset enabled)
Figure 3: Layout of all connectors, jumpers and status LEDs on the TC4+
board.
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CH2-
CH2+
CH1-
CH1+
CH4-
CH4+
CH3-
CH3+
TC4+
Analog In
Figure 4: Layout of the thermocouple channels on the TC3 board.
3 Connecting to your roaster
This section will briefly list how to connect the TC4+ to the most common
accessories. Figure 3 shows the location and layout of all connectors and status
LEDs on the TC4+. See the end of the section for a complete application
example.
3.1 Connecting to the Arduino
Stack the TC4+ shield on top of an Arduino Uno R3, or compatible. The long
pins on the underside of the TC4+ go into the corresponding headers on the
top side of the Arduino.
3.2 Connecting thermocouples
The TC4+ provides four thermocouple channels. These are provided in an 8pin screw terminal near the “north” edge of the board. Due to board layout
constraints, the order of the pins is not ascending, but in order CH2-, CH2+,
CH1-, CH1+, CH4-, CH4+, CH3-, CH3+. See Figure 4 for details.
Usually, you will want to use one K-type thermocouple probe each to measure
bean temperature (BT) and air temperature (ET). Connect ET to channel 1,
and BT to channel 2. Positive and negative wires need to be correct - if you see
wrong temperature readings, try reversing the wires. If you thermocouple probe
comes with a plug, remove it either by unscrewing if possible or else cutting it
off.
3.3 Connecting to DC power
The DC IN terminal can be connected to a DC power supply. This will supply
power to two things: Firstly, to the TC4+ and the connected Arduino. Secondly,
to a connected DC motor (or other DC load). If you intend to connect a DC
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fan
DC−
T C4+
DC+
Figure 5: A flyback diode across the motor.
motor, connecting a DC power supply is required. If not, this is optional - the
TC4+ and Arduino could alternatively be powered by USB.
The DC power supply should match the voltage of the DC motor. That is, if
your motor needs 20V, choose a 20V PSU. The rated current of the PSU must
match or exceed the power draw of the motor. If the motor draws 2A, choose a
PSU that is rated for at least 2A. The voltage of the PSU should also be within
the range of the on-board voltage regulator, which is 7-28V. If you need more
for your motor, replace the voltage regulator with an appropriate model.
Connect the power supply to the DC in screw terminal. Take care of correct
polarity: Positive goes to VIN, negative goes to GND.
3.4 Connecting to a DC motor
You can connect a DC load, like a fan motor, to the DC OUT terminal.
Important: You must also connect a suitable flyback diode. That is, a diode
that is connected across the motor terminals, in opposite direction to usual
current flow. See Figure 5. This is to prevent damage to the MOSFET. Either
solder an appropriate diode to the motor (preferred), or screw it into the screw
terminal together with the motor power cables. (Be careful of correct polarity,
or you will create a short!) Make sure the diode is rated appropriately. If your
motor was originally connected to a bridge rectifier, you might want to reuse
one of the diodes from the rectifier.
Important: DC motors can generate a lot of electrical noise, which can affect
thermocouple readings among other things. If your motor came with capacitors
or inductors connected to it, leave those in place, and connect the TC4+ to the
entire motor circuit. If you sourced a plain motor, take appropriate steps to
filter out noise.
3.5 Connecting a heating element
The TC4+ has two SSR drivers which can be used for heating elements. You
will need a DC-AC solid-state relay. Connect the DC side to OT1, taking care
of correct polarity. Connect the AC side of the SSR to the LIVE AC line going
to the heating element.
Important: If your popcorn machine came with a thermal fuse, make sure this
stays connected in series with the heating element. If it didn’t come with one or
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HC-05
STATE
RX
TX
GND
VCC
EN
HC-06
RX
TX
GND
VCC
BT HDR
RESET
TX / IO5
RX / IO4
GND
5V
BT HDR
RESET
TX / IO5
RX / IO4
GND
5V
Figure 6: Connection of the HC-05 (left) and HC-06 (right) Bluetooth modules.
you sourced your heating element separately, I strongly recommend connecting
a suitably placed thermal fuse in series with the heater.
Important: Powering your heating element without airflow might result in
near-instantaneous overheating.
Important: Exercise care when mains voltage is, or might be, present.
3.6 Connecting an AC fan
AC fans are slightly more complex to control. There is two options of interfacing
with them: A separate PWM dimmer module (recommended), or a zero-cross
detector (beyond the scope of this guide).
To control an AC fan via a PWM dimmer module, you will need a PWM dimmer module. One verified option is this: https://www.tindie.com/products/
bugrovs2012/pwm-ac-light-dimmer- module-50hz-60hz
To connect this, use a three-pin cable to connect the PWM header on the
PWM dimmer board to the TC4+. 5V goes to 5V, GND goes to GND. PWM
goes to IO3. The AC side of the PWM dimmer board connects to the mains,
and to the AC fan, respectively.
Important: Exercise care when mains voltage is, or might be, present.
3.7 Bluetooth Header
The board provides a 5-pin header for a HC-05 or HC-06 Bluetooth module.
This allows wireless roast monitoring and control. With a HC-05 (but not HC-
06), you can also wirelessly upload Arduino sketches. See Figure 6 for how to
connect either module. See the configuration section for details on how to set
up the connection.
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3.8 Application Example
The TC4+ board was designed to simplify control of popcorn machine based
home coffee roasters. In such a scenario, the board would be connected as
follows.
• The INPUT (GND / VIN) screw terminal connects to a DC power supply
unit.
• The FAN (DC+ / DC-) connects to the fan motor. A suitable flyback
diode would be soldered directly to the motor terminals.
• Thermocouple channel 1 connects to a thermocouple measuring the temperature of the incoming air (optional).
• Thermocouple channel 2 connects to a thermocouple measuring the temperature inside the roast chamber.
• The Bluetooth header connects to a Bluetooth module.
• The OT1 screw terminal connects to a solid state relay (SSR), which in
turn controls the AC live wire going to the heating element. A thermal
fuse in series with the heater is strongly recommended.
Figure 7 gives a schematic with all these connections.
3.9 Further Connectors, Jumpers & Status LEDs
Further to the connectors discussed, the TC4+ features the headers, jumpers
and status LEDs listed below.
• IO2, IO3 break out the Arduino’s IO2 and IO3 ports and GND. Note that
IO3 is also connected to the MOSFET.
• I2C provides two 4-pin I2C headers for displays etc.
• Arduino stackable headers provide all Arduino pins. Note that IO2, IO3,
IO9 and IO10 are in use for IO2, IO3, OT1, OT2, respectively. IO4 and
IO5 may be in use for the Bluetooth module.
• BT SEL and BT RST jumpers for configuring Bluetooth connection and
optional Bluetooth reset circuit.
• Status LEDs for Power On, OT1 and OT2.
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TC2 (bean temp)
Roast Chamber
HC-05
STATERXTX
- OT2 + - OT1 +
GND
VCC
EN
CH2- CH2+ CH1- CH1+ CH4- CH4+ CH3- CH3+
GND VIN
DC+ DC-
TC4+
TC1 (air temp)
heater
thermal fuse
fan
flyback diode
SSR
GND +8-28V
DC PSU
LIVE
NEUTRAL
AC
Figure 7: A typical application example of the TC4+ board. This shows the
TC4+ board connected to a DC PSU; a fan with flyback diode; a SSR controlling
a heater (with thermal fuse); a HC-05 Bluetooth module; and two thermocouples
measuring bean and air temperature.
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4 Software
4.1 Arduino sketch
The most commonly used Arduino sketch is aArtisanQ PID, available at https:
//github.com/greencardigan/TC4-shield/tree/master/applications/Artisan/
aArtisan_PID/trunk/src/aArtisanQ_PID For all the configurations discussed
in this guide, you will want to use this in PWM configuration mode.
4.2 Artisan
You will usually want to use Artisan on your host computer, available at https:
//artisan-scope.org/.
4.3 Bluetooth module
See separate guide for Bluetooth configuration.
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